The complications associated with the transportation and storage of particulate materials which can freeze and clump together during the colder periods of the year has become a major commercial problem. Such materials are transported and stored primarily in open vehicles and containers, accessible to potential ice generating precipitation including rain, sleet and snow. The problem is particularly acute in transportation of coal, iron ore and other minerals in open rail cars and trucks. As the loaded cars and trucks are moved across the country, the material in the zone immediately adjacent the outer walls of the vehicles gets cold faster than the main body of material. Moisture subsequently condenses in this zone and the material begins to aggregate as the moisture freezes, acting as a cement. This condensation, coupled with the moisture from rain, sleet and snow which tends to collect adjacent to the container walls causes a defined layer of material-incorporated ice to harden adjacent to and become attached to the walls. As much as 20 percent of the material may remain frozen in the car. The purchaser of the material has ordered 100 percent and received 80 percent Furthermore, the shipper has to pay to haul that 20 percent of the material back to the mining site. If the material freezes in uneven weight distributions, which it often does, the shipper cannot move the car until they have removed the rest of the material in order to keep the cars balanced and avoid potential derailments. This wall-adhering frozen portion therefor makes material unloading difficult through the normal automated procedures and requires people with chipping tools to enter the partially unloaded containers to manually remove the remaining iced layer stuck on the walls.
A problem also arises when moisture leaches corrosive compounds from the contained particulate materials, even at temperatures at and below freezing. Storage containers and vehicles such as rail cars and truck beds are made of iron containing metals which tend to rust and corrode excessively because of this corrosive moisture in contact with the walls. This corrosive action thereby shortens the expected lifetime of such containers and vehicles.
The compositions of this invention are also useful in de-icing and protecting external aircraft components from freezing during the period of time surrounding take-off. During severe cold weather conditions, the wings and body portions of aircraft will become coated with ice, sleet and snow and such build-up must be removed from the aircraft prior to take-off. In fact, plane crashes have occured because the build-up was sufficient to prevent the aircraft from gaining proper altitude after take-off. Various systems are presently used to prevent such build-ups and to remove layers of ice, sleet and snow immediately prior to take-off. However, no completely satisfactory system has been developed.
The prior art details several attempts at correcting these problems. Some inventors have attempted to correct the problems only after the particulate material is already frozen to the container walls. U.S. Pat. No. 4,388,203 discloses compositions and methods for melting already frozen material by applying de-icing compositions to the surface of particulate materials such as coal. These compositions also may be used on frozen surfaces such as rail cars to thaw accumulated frozen water. This is inefficient as one would have to wait for each container of material to thaw at every transfer point before unloading and use.
Other inventors have treated the materials themselves prior to loading into the vehicles or storage containers. U.S. Pat. No. 4,426,409 discloses freeze protection polymer systems for use in spraying particles such as coal to reduce the cohesive strength of such particles. U.S. Pat. No. 5,079,036 discloses a brine freeze control agent which is applied to particulate materials such as coal or mineral ores to inhibit freezing aggregation. This is uneconomical when one considers the millions of tons of such materials shipped every year and the additional cost involved in treating the necessary materials.
A few inventors have attempted to solve the problem through preventative treatment of the containers prior to the addition of the particulate material. In Nimerick U.S. Pat. No. 4,439,337, a viscous mixture is applied to the metal surface before loading of the materials in order to freeze proof those surfaces. Other attempts have been made to control and inhibit the freeze agglomeration of particulate materials during transportation and all such attempts have limitations ranging from difficulty of application to low cost-performance ratios. Many of these solutions contain ethylene glycol, sodium chloride and other substances which require special disposal methods or adversely affect the environment. The aircraft anti-icing fluid in U.S. Pat. No. 4,698,172 is an ethylene glycol solution thickened with gel forming carrageenans.